Light emitting diode device having electrode with low illumination side and high illumination side

ABSTRACT

A high-brightness vertical light emitting diode (LED) device includes an outwardly located metal electrode having a low illumination side and a high illumination side. The LED device is formed by: forming the metal electrode on an edge of a surface of a LED epitaxy structure using a deposition method, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), evaporation, electro-plating, or any combination thereof; and then performing a packaging process. The composition of the LED may be a nitride, a phosphide or an arsenide. The LED has the following advantages: improving current spreading performance, reducing light-absorption of the metal electrode, increasing brightness, increasing efficiency, and thereby improving energy efficiency. The metal electrode is located on the edge of the device and on the light emitting side. The metal electrode has two side walls, among which one side wall can receive more emission light from the device in comparison with the other one.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 12/939,142 filed Nov. 3,2010, U.S. Pat. No. 8,450,758 B2.

BACKGROUND

Currently, LED is widely applied in our daily life due to itscharacteristics of low production cost, easy fabrication, small size,low power consumption and high efficiency, for example, in the fields ofcell phones, electric boards, electric torches, traffic lights and soon. Nevertheless, improvements in the luminous efficiency and brightnessof a LED are pursued continuously.

Recently, high-brightness LEDs using nitrides and phosphides have beendeveloped, which can not only emit red, green and blue light but alsoproduce light in various colors and white light. At present, LEDlighting applications are developed enthusiastically by industry. In theearly stage of manufacturing development, multiple LEDs were combined toform an array, so as to achieve high output power. However, in terms ofmanufacturing, a LED device including a LED array is more complicatedthan a single LED device with high output power. Therefore, the cost ofmanufacturing the LED array device is higher and the stable reliabilityis less likely to be achieved.

One method to increase the power and luminous flux of a LED is toincrease the size and luminous surface area thereof. However, thesemiconductor material layer used in a conventional LED usually has poorconductivity, such that electric current cannot be spread effectivelyand uniformly over an active layer from a contact. Therefore, some areasinside the LED can produce high electric current density phenomenon,thereby affecting the whole brightness, even leading to earlydeterioration in the proximity of the active layer. As a result, theservice life of the LED is reduced significantly.

FIG. 1A is a top view of a configuration of a conventional small-sizevertical LED device 100. FIG. 1B is a cross-sectional view of theconfiguration of the LED device 100 shown in FIG. 1A. FIG. 2 is a topview of a configuration of a conventional large-size vertical LED device200. With reference to FIG. 1B, the configuration of the conventionalsmall-size LED device 100 typically includes a first electrode 109, aconductive substrate layer 108 formed on the first electrode 109, areflective mirror layer 106 formed on the conductive substrate layer108, a first conductivity type semiconductor layer 104 formed on thereflective mirror layer 106, an active layer 103 (or referred as anemission layer) formed on the first conductivity type semiconductorlayer 104, a second conductivity type semiconductor layer 102 formed onthe active layer 103, and a second metal electrode 101 formed on thesecond conductivity type semiconductor layer 102. As shown in FIG. 1A,in the small-size vertical LED device 100, the second metal electrode101 is located on the center of the second conductivity typesemiconductor layer 102. Furthermore, additional metal wires are notrequired due to the small size and the good current spreadingperformance of the LED device 100.

For a conventional large-size vertical LED device, a major reason ofaffecting the luminous efficiency of the LED device is the failure tospread electric current uniformly, so it is contemplated to increase thethickness of a semiconductor material layer so as to increase theconductivity. For the small-size LED (less than about 0.25 mm²) shown inFIGS. 1A and 1B, its brightness and current spreading performance cancertainly be improved by this method. However, the increased thicknessof the semiconductor material layer may not only increase productioncosts but also lead to stress problems. Therefore, it is impossible tounlimitedly increase the thickness of the semiconductor material layerto comply with the current spreading performance requirement of alarge-size LED device. As a result, for the large-size device shown inFIG. 2, a satisfactory performance cannot be achieved merely byincreasing the thickness of the semiconductor material layer. This isbecause when the size of a LED device is increased, it becomes moreunlikely to uniformly spread electric current over the semiconductormaterial layer from an n-type contact or a p-type contact. It can beseen that the size of a LED is substantially limited by the currentspreading characteristic of the semiconductor material layer.

As shown in FIG. 2, in a conventional large-size vertical LED device 200having a first conductivity type semiconductor layer 204 and areflective mirror layer 206, a second metal electrode pad area 210 islocated on the center of a second conductivity type semiconductor layer202, which generally utilizes radial metal electrodes 201 to increasethe current spreading performance. However, most of the outlines ofcommon LED devices are squares or rectangles, therefore it is difficultnot only to place each radial metal wire on an emission layer such thatthe best current spreading performance can be achieved, but also toensure that the adjacent radial metal wires have constant intervaltherebetween. In addition, both sides of the metal electrode are highillumination sides, which tend to absorb emission light, therebydecreasing brightness. As shown in FIGS. 3A and 3B, for otherconventional large-size vertical LED devices 200A and 200B, both sidesof their metal electrodes are high illumination sides, which also tendto absorb emission light, thereby decreasing brightness. Therefore,conventional LED devices still generally have the following problemsincluding uneven current density, low light extraction efficiency,unsatisfactory brightness, unsatisfactory efficiency, short servicelife, and so on, which are to be solved.

SUMMARY

In view of the above problems, an improved vertical LED device isprovided, which has the higher output brightness and efficiency incomparison with conventional LED devices. In addition, the LED devicecan fully fulfill the contemporary demand for high energy efficiencywithout increasing production costs. Furthermore, the manufacturingmethod of the present LED device involves no complicated technique,which means the method is economically beneficial.

In order to solve the above problems and achieve the above goals, an LEDdevice is provided having improved current spreading performance andreduced light-absorption of a metal electrode.

One aspect is to provide a vertical light emitting diode (LED) devicehaving an outwardly located metal electrode, the LED device including: afirst electrode, a conductive substrate layer formed on the firstelectrode, a reflective mirror layer formed on the conductive substratelayer, a first conductivity type semiconductor layer formed on thereflective mirror layer, an active layer formed on the firstconductivity type semiconductor layer, a second conductivity typesemiconductor layer formed on the active layer, a second metal electrodeformed on the second conductivity type semiconductor layer and beinglocated on an edge of the second conductivity type semiconductor layer,two sides of the second metal electrode being a high illumination sideand a low illumination side respectively, wherein the low illuminationside is located beyond the width scope of the reflective mirror layer.

The current spreading performance of a vertical LED device can beoptimized and the light-absorption of a metal electrode can be reducedby applying an outwardly located metal electrode, thereby increasing thebrightness, efficiency and service life of the LED device, and reducingenergy costs.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, like elements are represented by likenumerals.

FIG. 1A shows a top view of a conventional small-size vertical LEDdevice;

FIG. 1B shows a cross-sectional view of conventional small-size verticalLED device;

FIG. 2 shows a top view of a conventional large-size vertical LEDdevice;

FIG. 3A shows both of a top view and a detailed cross-sectional view ofa conventional large-size vertical LED device, both sides of the metalelectrode thereof being high illumination sides;

FIG. 3B shows both of a top view and a detailed cross-sectional view ofanother conventional large-size vertical LED device, both sides of themetal electrode thereof being high illumination sides;

FIG. 4 shows a top view of a large-size vertical LED device according toone embodiment, wherein the die size is 1 mm²;

FIG. 5 shows both of a top view and a cross-sectional view of thelarge-size vertical LED device shown in FIG. 4;

FIG. 6 illustrates a three dimensional view of the large-size verticalLED device shown in FIG. 4;

FIG. 7 shows both of a top view and a detailed cross-sectional view of alarge-size vertical LED device according to one embodiment, wherein thedie size is 1 mm²;

FIG. 8 shows both of a top view and a detailed cross-sectional view of alarge-size vertical LED device according to another embodiment, whereinthe die size is 1 mm²;

FIG. 9 shows both of a top view and a detailed cross-sectional view of alarge-size vertical LED device according to yet another embodiment,wherein the die size is 1 mm²;

FIG. 10 shows both of a top view and a detailed cross-sectional view ofa large-size vertical LED device according to another embodiment,wherein the die size is 1 mm²;

FIG. 11 shows a top view of a large-size vertical LED device accordingto another embodiment, wherein the die size is 0.6 mm²;

FIG. 12 shows both of a top view and a cross-sectional view of thelarge-size vertical LED device shown in FIG. 11;

FIG. 13 shows both of a top view and a cross-sectional view of asmall-size vertical LED device according to one embodiment, wherein thedie size is 0.1 mm²;

FIGS. 14A-14F, 15A-15F, 16A-16F, 17A-17F, 18A-18F, and 19A-19Frespectively show top views of large-size vertical LED devices accordingto other embodiments, wherein their die sizes are more than 0.3 mm²;

FIGS. 20A-20D respectively show top views of vertical LED devicesaccording to other embodiment, wherein their die sizes are less than 0.3mm²;

FIGS. 21A-21I respectively show top views of vertical LED devices havinga rectangular die shape according to other embodiments;

FIGS. 22A-22B show side views of the large-size vertical LED devices;FIGS. 23A-23B show side views of the small-size vertical LED shown inFIG. 13;

FIGS. 24A-24B show side views of the vertical LED device having arectangular die shape shown in FIG. 21A; and

FIG. 25 shows comparison results between a large-size (1 mm²) verticalnitride-based (gallium nitride) blue LED device 300 and four LED deviceswith prior art designs A, B, C and D in terms of their brightness.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments are described hereinafter, including variousembodiments of vertical LED devices in which the current spreadingperformance of a semiconductor layer and the light-absorption propertyof a metal electrode have been modified, thereby achieving betterbrightness, efficiency and service life in comparison with conventionalLED devices.

FIG. 4 shows a top view of a large-size vertical GaN-based (galliumnitride) LED device 300. FIG. 5 shows both of a top view and across-sectional view of the LED device 300 shown in FIG. 4. FIG. 6illustrates a three dimensional view of the LED device 300 shown in FIG.4. In this embodiment, the size of the n-type (second conductivity type)semiconductor layer 302 is 1 mm². The large-size vertical LED device 300includes a first electrode 309, a conductive substrate layer 308 formedon the first electrode 309, a reflective mirror layer 306 formed on theconductive substrate layer 308, a p-type (first conductivity type)semiconductor layer 304 formed on the reflective mirror layer 306, anactive layer 303 (also referred as “an emission layer”) formed on thep-type (first conductivity type) semiconductor layer 304, an n-type(second conductivity type) semiconductor layer 302 formed on the activelayer 303, and a second metal electrode 301 formed on the n-type (secondconductivity type) semiconductor layer 302, in which the second metalelectrode 301 is provided on an edge of the n-type semiconductor layer302, and two sides of the second metal electrode 301 are a highillumination side 301′ and a low illumination side 301″, respectively.The low illumination side 301″ is located beyond the width scope W ofthe reflective mirror layer 306. In other words, the low illuminationside 301″ is not covered by the reflective mirror layer 306. Three metalelectrode wires are provided inwardly to connect with the second metalelectrode 301. It should be noted that the numbers of the inwardlyprovided metal electrode wires can be adjusted to comply with theoutline and size of the entire LED device or to meet a request. Partialareas of a surface of the second conductivity type semiconductor layercan be patterned to improve light extraction efficiency. In addition,the LED device 300 further includes a metal pad area 310, as shown inFIGS. 4 and 6, used as an electrical contact. It should be noted thatthe metal pad area 310, used as the electrical contact, shown in thedrawings is intended for purposes of illustration only and is notintended to limit the scope of the claims. The numbers of the metal padarea 310 can be adjusted according to actual demands. Furthermore, theLED device 300 may include a conductive transparent layer (not shown),which is provided between the second conductivity type semiconductorlayer 302 and the second metal electrode 301.

FIG. 7 shows both of a top view and a cross-sectional view of alarge-size vertical GaN-based (gallium nitride) LED device 400 accordingto another embodiment. In the LED device 400, a surface of the secondconductivity type semiconductor layer 302 near the high illuminationside is roughed to increase light extraction efficiency. FIG. 8 showsboth of a top view and a cross-sectional view of a large-size verticalLED device 400′ according to yet another embodiment. In the LED device400′, the entire surface of the second conductivity type semiconductorlayer 302 is roughed to further increase light extraction efficiency. Asurface of the second conductivity type semiconductor layer 302 can beroughed by using domes/beads or using a wet/dry etching technique, butnot limited to this.

FIG. 9 shows both of a top view and a cross-sectional view of alarge-size vertical LED device 500 according to another embodiment. TheLED device 500 further includes a protective layer 311, which is used toprotect the reflective mirror layer 306, so as to prevent the reflectivemirror layer 306 from being oxidized and resulting in brightnessdecrease. A material of the protective layer 311 may be at least onematerial selected from the group consisting of Ni, W, Mo, Pt, Ta, Rh,Au, V, WTi, TaN, SiO₂, SiN_(x), Al₂O₃, AN, ITO and Ni—Co. The protectivelayer 311 can be formed by using at least one of the following methods:PVD, CVD, evaporation, sputtering, electro-plating, electroless plating,coating, printing, or any combination thereof. Although only the surfaceof the second conductivity type semiconductor layer 302 near the highillumination side is roughed according to FIG. 9, the entire surface ofthe second conductivity type semiconductor layer 302 can be roughed ifnecessary.

FIG. 10 shows both of a top view and a cross-sectional view of alarge-size vertical LED device 600 according to another embodiment. Inthe LED device 600, an optical transparent layer 312 is provided betweena reflective mirror layer 314 and the first conductivity typesemiconductor layer 304 to form an omni-directional reflector. Thereflective mirror layer 314 can be a high-reflectivity metal layer, or adistributed Bragg reflector (DBR), so as to increase external quantumefficiency. The method of manufacturing the reflective mirror layer 314can be a conventional method, such as PVD, CVD, evaporation, sputtering,electro-plating, electroless plating, coating, printing, or anycombination thereof. In one embodiment, a reflective mirror layer canhave a single- or multi-layer structure. In addition, a material of thereflective mirror layer may be one metal selected from the following:Ag/Ni, Ni/Ag/Ni/Au, Ag/Ni/Au, Ag/Ti/Ni/Au, Al, Ti/Al, Ni/Al, Au, anycombination of at least two thereof, or an alloy thereof containing Ag,Au, Ni, Cr, Pt, Pd, Rh, Cu, W, In, Pd, Zn, Ge, Bi, AlSi, or Al. Amaterial of the distributed Bragg reflector may be, for example, SiO₂,TiO₂, MgO, Al₂O₃, ITO, ZnO, SiN_(x), or any combination of at least twothereof. A material of the omni-directional reflector may be, forexample, SiO₂, TiO₂, MgO, Al₂O₃, ITO, ZnO, SiN_(x), or any combinationof at least two thereof. The conductive substrate layer may be a metalor a semiconductor material, such as silicon, GaP, SiC, GaN, AN, GaAs,InP, AlGaAs, and ZnSe, or any combination of at least two thereof.Likewise, the conductive substrate layer can be formed by using aconventional method, such as PVD, CVD, evaporation, sputtering,electro-plating, electroless plating, coating, printing, wafer bonding,or any combination thereof; its thickness may be from 10 μm to 1000 μmbased on various requests. Although only the surface of the secondconductivity type semiconductor layer 302 near the high illuminationside is roughed according to FIG. 10, the entire surface of the secondconductivity type semiconductor layer 302 can be roughed if necessary.

FIG. 25 shows comparison results between a large-size (1 mm²) verticalnitride-based (gallium nitride) blue LED device 300 according to oneembodiment and four LED devices with prior-art designs A, B, C and D interms of their brightness (light output power). The five LED deviceswith various designs are made from the same epitaxy wafer, usingidentical frames, and finally packed by silica gels via totallyidentical procedures to obtain the products. In Table 1, the brightness(light output power) was measured by an integrating sphere, which iswell known to those skilled in the art, and thus detailed descriptionsthereof are omitted here. As shown in Table 1, the LED device has higheroutput power in comparison with other prior-art LED devices.

FIG. 11 shows a top view of a large-size (0.6 mm²) vertical GaN-based(gallium nitride) LED device 700 according to another embodiment. FIG.12 shows both of a top view and a cross-sectional view of the LED device700 shown in FIG. 11. The LED device 700 includes a second metalelectrode 701, a second conductivity type semiconductor layer 702, anactive layer (emission layer) 703, a first conductivity typesemiconductor layer 704, a reflective mirror layer 706, a conductivesubstrate layer 708, and a first electrode 709, in which the size of thesecond conductivity type semiconductor layer 702 is 0.6 mm², and thesecond metal electrode 701 is provided on an edge of the secondconductivity type semiconductor layer 702. Two sides of the second metalelectrode 701 are a high illumination side 701′ and a low illuminationside 701″ respectively, wherein the low illumination side 701″ islocated beyond the width scope W of the reflective mirror layer 706. Inother words, the low illumination side 701″ is not covered by thereflective mirror layer 706. Furthermore, in this embodiment, a metalpad area 710 used as an electrical contact is provided.

FIG. 13 shows both of a top view and a cross-sectional view of asmall-size vertical GaN-based (gallium nitride) LED device 800 accordingto one embodiment. The LED device 800 includes a second metal electrode801, a second conductivity type semiconductor layer 802, an active layer(emission layer) 803, a first conductivity type semiconductor layer 804,a reflective mirror layer 806, a conductive substrate layer 808, and afirst electrode 809. In this embodiment, the size of the secondconductivity type semiconductor layer 802 is 0.1 mm². The small-sizevertical LED device 800 includes a first electrode 809, a conductivesubstrate layer 808 formed on the first electrode 809, a reflectivemirror layer 806 formed on the conductive substrate layer 808, a firstconductivity type semiconductor layer 804 formed on the reflectivemirror layer 806, an active layer 803 (also referred as “an emissionlayer”) formed on the first conductivity type semiconductor layer 804, asecond conductivity type semiconductor layer 802 formed on the activelayer 803, and a second metal electrode 801 formed on the secondconductivity type semiconductor layer 802, in which the second metalelectrode 801 is provided on an edge of the second conductivity typesemiconductor layer 802. Two sides of the second metal electrode 801 area high illumination side 801′ and a low illumination side 801″respectively, wherein the low illumination side 801″ is located beyondthe width scope W of the reflective mirror layer 806. In other words,the low illumination side 801″ is not covered by the reflective mirrorlayer 806.

Preferably, the first conductivity type semiconductor layer (304, 704,and 804) is p-type, and the second conductivity type semiconductor layer(302, 702, and 802) is n-type. An n-type semiconductor layer has betterconductivity, and thus less numbers of metal electrodes are required, soas to reduce shading and increase brightness. Furthermore, preferably,doping levels may range from 1×10¹⁵ cm⁻³ to 1×10²² cm⁻³, and a thicknessof the semiconductor layer may be 0.3 μm to 100 μm. In one embodiment, afirst conductivity type semiconductor layer, a second conductivity typesemiconductor layer and an active layer may be formed by using aconventional method, such as metal-organic chemical vapor deposition(MOCVD), vapor phase epitaxy (VPE), and molecular beam epitaxy (MBE),which are well known to those skilled in the art and need not bedescribed in further detail. A configuration of the active layer may beselected from the group consisting of double-hetero and quantum-wellstructures containing aluminum gallium indium nitrides((Al_(x)Ga_(1-x))_(y)In_(1-y)N; 0 x 1; 0 y 1), or selected from thegroup consisting of double-hetero and quantum-well structures containingaluminum gallium indium phosphides ((Al_(x)Ga_(1-x))_(y)In_(1-y)P; 0 x1; 0 y 1), or from the group consisting of double-hetero andquantum-well structures containing aluminum gallium arsenides(Al_(x)Ga_(1-x)As; 0 x 1). The second metal electrode (301, 701, and801) and the first electrode (309, 709, and 809) may be formed by usinga conventional method, such as PVD, CVD, evaporation, sputtering,electro-plating, electroless plating, coating, printing, or anycombination thereof. For example, the second metal electrode may have asingle- or multiple-layer structure containing one of the followingmaterials: Cr/Au, Cr/Al, Cr/Pt/Au, Cr/Ni/Au, Cr/Al/Pt/Au, Cr/Al/Ni/Au,Al, Ti/Al, Ti/Au, Ti/Al/Pt/Au, Ti/Al/Ni/Au, Ti/Al/Pt/Au, WTi, Al/Pt/Au,Al/Pt/Al, Al/Ni/Au, Al/Ni/Al, Al/W/Al, Al/W/Au, Al/TaN/Al, Al/TaN/Au,Al/Mo/Au, or a alloy consisting of at least two thereof, or othersuitable conductive materials.

The width of the second metal electrode may be 1 μm to 50 μm, preferably3 μm to 30 μm. Although a broader metal electrode wire may spreadelectric current more effectively, it can obstruct or absorb moreemission light from an n-type layer. One solution for this is to providea current blocking structure configured to prevent the emission lightfrom the n-type layer from being obstructed or absorbed by the metalelectrode wire. However, if the broader metal electrode wire isemployed, the size of the current blocking structure is required to beincreased accordingly, thereby reducing the emission area of the activelayer, and thus decreasing the amount of light through the active layer.A space between the second metal electrode wires may be 50 μm to 600 μm.The current spreading performance becomes better when the space isadequate. However, a contact area can be reduced when the space betweenthe metal electrode wires is larger, thereby adversely affecting theoperation voltage. Preferably, a total surface area of the second metalelectrode occupies less than 25% of a surface area of the secondconductivity type semiconductor layer, and a contact area between thereflective mirror layer and the first conductivity type semiconductorlayer occupies more than 75% of a surface area of the first conductivitytype semiconductor layer. A thickness of the second metal electrode wiremay be 0.1 μm to 50 μm, preferably 1 μm to 10 μm. A thicker second metalelectrode has a lower series resistance, but the correspondingmanufacturing time and costs are inevitably increased.

It should be noted that the aforesaid materials of the second metalelectrode are intended for purposes of illustration only and are notintended to limit the scope of the claims.

FIGS. 14A-14F, 15A-15F, 16A-16F, 17A-17F, 18A-18F, and 19A-19Frespectively show top views of large-size vertical LED devices accordingto other embodiments, wherein their die sizes are more than 0.3 mm².FIGS. 20A-20D respectively show top views of vertical LED devicesaccording to other embodiments, wherein their die sizes are less than0.3 mm². FIGS. 21A-21I respectively show top views of vertical LEDdevices having a rectangular die shape according to other embodiments.FIGS. 22A-22B show side views of the large-size vertical LED devices,such as the LED devices shown in FIGS. 4-12, 14A-14F, 15A-15F, 16A-16F,17A-17F, 18A-18F, and 19A-19F. FIGS. 23A-23B show side views of thesmall-size vertical LED shown in FIG. 13. FIGS. 24A-24B show side viewsof the vertical LED device having a rectangular die shape shown in FIG.21A.

The present device is characterized in that a metal electrode of avertical LED device is provided on a semiconductor layer to form anoutwardly located metal electrode. The current spreading performance ofthe vertical LED device having a cube or rectangular shape can beoptimized and the light-absorption of the metal electrode can be reducedvia the configuration of providing the metal electrode on the edge,thereby increasing the brightness, efficiency, and service life of theLED devices, and thus displaying a superior performance over otherprior-art LED devices.

It should be understood by those skilled in the art that the foregoingdescription only shows the preferred embodiments, the same is to beconsidered as illustrative and not restrictive in character. Variousequivalent changes and modifications can be made without departing fromthe spirit and scope of present disclosure, which are therefore intendedto be embraced in the appended claims.

What is claimed is:
 1. A light emitting diode device comprising: aconductive base having a first electrode; a reflective mirror layer onthe conductive base having a width scope W, a first conductivity typesemiconductor layer on the reflective mirror layer, an active layer onthe first conductivity type semiconductor layer configured to produceemission light, a second conductivity type semiconductor layer on theactive layer having a surface, an outline, a surface area and an edge,and a second electrode comprising a wire on the surface of the secondconductivity type semiconductor layer having a width and a surface area,the wire within the outline of the second conductivity typesemiconductor layer and with the surface area of the wire selectedrelative to the surface area of the second conductivity typesemiconductor layer to provide a desired current spreading across theactive layer, the wire having a low illumination side located outside ofthe width scope W of the reflective mirror layer and formed along theedge of the second conductivity type semiconductor layer, and a highillumination side spaced from the low illumination side by the width ofthe wire, the high illumination side configured to receive at least someof the emission light reflected from the reflective mirror layer, thelow illumination side configured to reduce light absorption of thesecond electrode.
 2. The device of claim 1 wherein the second electrodefurther comprises a contact pad on the surface of second conductivitytype semiconductor layer and an inner wire in electrical contact withthe wire and with the contact pad.
 3. The device of claim 1 wherein thesecond conductivity type semiconductor layer and the wire each have agenerally rectangular or square outline.
 4. The device of claim 1wherein the wire has a width of from 1 μm to 50 μm.
 5. A light emittingdiode device comprising: a conductive base having a first electrode; areflective mirror layer on the conductive base, a first conductivitytype semiconductor layer on the reflective mirror layer, an active layeron the first conductivity type semiconductor layer configured to produceemission light, a second conductivity type semiconductor layer on theactive layer having a surface, an outline and an edge, and a secondelectrode comprising a wire on the surface of the second conductivitytype semiconductor layer, the wire having a width and a surface areawithin the outline of the second conductivity type semiconductor layer,with the surface area of the wire selected relative to the surface areaof the second conductivity type semiconductor layer to provide a desiredcurrent spreading across the active layer, the wire having a highillumination side configured to absorb reflected emission light from thereflective mirror layer, the wire having a low illumination side formedalong the edge of the second conductivity type semiconductor layer andseparated from the high illumination side by the width of the wire, thelow illumination side not covered by the reflective mirror layer suchthat the emission light does not reflect from the reflective mirrorlayer onto the low illumination side, the second electrode furthercomprising a contact pad on the surface of second conductivity typesemiconductor layer in electrical communication with the wire via aplurality of inner wires arranged in a pattern within the outline. 6.The device of claim 5 wherein a first surface area of the reflectivemirror layer is more than 75% and less than 100% of a second surfacearea of the first conductivity type semiconductor layer.
 7. The deviceof claim 5 wherein the wire has a generally rectangular or square shapecorresponding to the outline of the second conductivity typesemiconductor layer.
 8. The device of claim 5 wherein the reflectivemirror layer has a width scope W and the low illumination side islocated outside of the width scope W.
 9. A light emitting diode devicecomprising: a conductive base having a first electrode; a reflectivemirror layer on the conductive base having a width scope W, a firstconductivity type semiconductor layer on the reflective mirror layer, anactive layer on the first conductivity type semiconductor layerconfigured to produce emission light, a second conductivity typesemiconductor layer on the active layer having a surface and an edge,and a second electrode on the surface of the second conductivity typesemiconductor layer comprising an outer wire having a width and asurface area formed along the edge, with the surface area of the outerwire selected relative to the surface area of the second conductivitytype semiconductor layer to provide a desired current spreading acrossthe active layer, the outer wire having a high illumination side and alow illumination side located outside of the width scope W of thereflective mirror layer and separated from the high illumination side bythe width of the outer wire, with the low illumination side configuredto absorb less reflected emission light from the reflective mirror layerthan the high illumination side, the second electrode further comprisinga plurality of inner wires in electrical communication with the outerwire in a pattern on the surface of the second conductivity typesemiconductor layer.
 10. The device of claim 9 wherein the highillumination side is located outside the width scope W.
 11. The deviceof claim 9 wherein the reflective mirror layer has a first surface areaand the first conductivity type semiconductor layer has a second surfacearea less than the first surface area.